It is known in the art that suction rolls are used in paper machines on the one hand to gather water from a paper web, on the other hand to direct the paper web in the roller groups. By setting a vacuum inside the mantle of the perforated suction roll, the paper web can be maintained on the surface of the suction roll. The necessary vacuum is produced by vacuum chambers, which are confined between the mantle and the suction box with sealing devices that cover the whole of the operating length of the suction roll.
These sealing devices each have a seal that extends to the inner face of the mantle, and there are two or more of them inside one suction roll. The seal is quickly used up when constantly pressed against the inner face of the mantle. Several pressing and regulation devices have been developed primarily for the purpose of reducing seal wear. For example, a sealing construction presented in FI patent application number 955275 includes loading hoses. Therein, the seal is pressed onto the mantle with one loading hose, and it is slightly pressed back with the other hose locking the seal into place. The principle is thus to lock the seal a small distance away from the mantle after the starting of the suction roll, whereby seal wear is reduced.
Due to the bend of the suction box, the elastic limit of the seal comes quickly to an end. One of the problems of the present seals is that they provide for only a small elastic movement length. It has not been possible to reduce the scale of the suction box and therefore the whole suction roll. It has only been possible to allow the suction box a slight bend.
In order to reduce the wearing of seals, the above-mentioned known solution has been carried out in a very complex way. Loading devices that include several components add to the risk of malfunctions. In addition, loading devices need to be manufactured accurately in order to function, which adds to the manufacturing and servicing expenses and further to the risk of malfunctions. The operating distance of loading devices is also limited, whereby they are only suited to seals of a certain height.